net/sctp: use-after-free in __sctp_connect

[Dmitry Vyukov]

Hello,

The following program causes use-after-free in __sctp_connect:

// autogenerated by syzkaller (http://github.com/google/syzkaller)
#include <unistd.h>
#include <sys/syscall.h>
#include <string.h>
#include <stdint.h>
#include <pthread.h>

long r[13];

void *thr(void *arg)
{
        switch ((long)arg) {
        case 0:
                r[0] = syscall(SYS_mmap, 0x20000000ul, 0x20000ul,
0x3ul, 0x32ul, 0xfffffffffffffffful, 0x0ul);
                break;
        case 1:
                r[1] = syscall(SYS_socket, 0xaul, 0x1ul, 0x84ul, 0, 0, 0);
                break;
        case 2:
                memcpy((void*)0x2000b000,
"\x0a\x00\x33\xe0\x49\xd0\x2e\x70\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01\x4c\x37\xff\xc4",
28);
                r[3] = syscall(SYS_bind, r[1], 0x2000b000ul, 0x1cul, 0, 0, 0);
                break;
        case 3:
                r[4] = syscall(SYS_dup2, r[1], r[1], 0, 0, 0, 0);
                break;
        case 4:
                *(uint64_t*)0x200177ed = (uint64_t)0x0;
                *(uint64_t*)0x200177f5 = (uint64_t)0x2710;
                r[7] = syscall(SYS_setsockopt, r[4], 0x1ul, 0x15ul,
0x200177edul, 0x10ul, 0);
                break;
        case 5:
                *(uint16_t*)0x2000b008 = (uint16_t)0x2;
                *(uint16_t*)0x2000b00a = (uint16_t)0xbab;
                *(uint32_t*)0x2000b00c = (uint32_t)0xffffffff;
                r[11] = syscall(SYS_setsockopt, r[4], 0x84ul, 0x6eul,
0x2000b000ul, 0x1cul, 0);
                break;
        case 6:
                r[12] = syscall(SYS_shutdown, r[4], 0x1ul, 0, 0, 0, 0);
                break;
        }
        return 0;
}

int main()
{
        long i;
        pthread_t th[7];

        memset(r, -1, sizeof(r));
        for (i = 0; i < 7; i++) {
                pthread_create(&th[i], 0, thr, (void*)i);
                usleep(10000);
        }
        for (i = 0; i < 7; i++) {
                pthread_create(&th[i], 0, thr, (void*)i);
                if (i%2==0)
                        usleep(10000);
        }
        usleep(100000);
        return 0;
}

==================================================================
BUG: KASAN: use-after-free in __sctp_connect+0xb23/0xb90 at addr
ffff8800605febb8
Read of size 4 by task syz-executor/15263

INFO: Allocated in sctp_association_new+0x6f/0x1da0 age=0 cpu=3 pid=15267
[<      none      >] ___slab_alloc+0x486/0x4e0 mm/slub.c:2468
[<      none      >] __slab_alloc+0x66/0xc0 mm/slub.c:2497
[<     inline     >] slab_alloc_node mm/slub.c:2560
[<     inline     >] slab_alloc mm/slub.c:2602
[<      none      >] kmem_cache_alloc_trace+0x284/0x310 mm/slub.c:2619
[<     inline     >] kmalloc include/linux/slab.h:458
[<     inline     >] kzalloc include/linux/slab.h:602
[<      none      >] sctp_association_new+0x6f/0x1da0 net/sctp/associola.c:302
[<      none      >] __sctp_connect+0x4ec/0xb90 net/sctp/socket.c:1161
[<      none      >] __sctp_setsockopt_connectx+0x198/0x1d0
net/sctp/socket.c:1328
[<     inline     >] sctp_setsockopt_connectx net/sctp/socket.c:1360
[<      none      >] sctp_setsockopt+0x226/0x3630 net/sctp/socket.c:3728
[<      none      >] sock_common_setsockopt+0x95/0xd0 net/core/sock.c:2642
[<     inline     >] SYSC_setsockopt net/socket.c:1752
[<      none      >] SyS_setsockopt+0x158/0x240 net/socket.c:1731
[<      none      >] entry_SYSCALL_64_fastpath+0x16/0x7a
arch/x86/entry/entry_64.S:185

INFO: Freed in sctp_association_put+0x150/0x250 age=0 cpu=3 pid=15267
[<      none      >] __slab_free+0x1fc/0x320 mm/slub.c:2678
[<     inline     >] slab_free mm/slub.c:2833
[<      none      >] kfree+0x2a8/0x2d0 mm/slub.c:3662
[<     inline     >] sctp_association_destroy net/sctp/associola.c:424
[<      none      >] sctp_association_put+0x150/0x250 net/sctp/associola.c:860
[<      none      >] sctp_wait_for_connect+0x37c/0x4f0 net/sctp/socket.c:7067
[<      none      >] __sctp_connect+0x905/0xb90 net/sctp/socket.c:1215
[<      none      >] __sctp_setsockopt_connectx+0x198/0x1d0
net/sctp/socket.c:1328
[<     inline     >] sctp_setsockopt_connectx net/sctp/socket.c:1360
[<      none      >] sctp_setsockopt+0x226/0x3630 net/sctp/socket.c:3728
[<      none      >] sock_common_setsockopt+0x95/0xd0 net/core/sock.c:2642
[<     inline     >] SYSC_setsockopt net/socket.c:1752
[<      none      >] SyS_setsockopt+0x158/0x240 net/socket.c:1731
[<      none      >] entry_SYSCALL_64_fastpath+0x16/0x7a
arch/x86/entry/entry_64.S:185

INFO: Slab 0xffffea0001817e00 objects=7 used=3 fp=0xffff8800605fa3b0
flags=0x5fffc0000004080
INFO: Object 0xffff8800605feb10 @offset=27408 fp=0x          (null)
CPU: 2 PID: 15263 Comm: syz-executor Tainted: G    B           4.4.0+ #237
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
 00000000ffffffff ffff88003717f8f0 ffffffff8290ea2d ffff88003e806a00
 ffff8800605feb10 ffff8800605f8000 ffff88003717f920 ffffffff81730904
 ffff88003e806a00 ffffea0001817e00 ffff8800605feb10 dffffc0000000000
Call Trace:
 [<ffffffff81739e1e>] __asan_report_load4_noabort+0x3e/0x40
mm/kasan/report.c:294
 [<ffffffff85925803>] __sctp_connect+0xb23/0xb90 net/sctp/socket.c:1217
 [<ffffffff85925a08>] __sctp_setsockopt_connectx+0x198/0x1d0
net/sctp/socket.c:1328
 [<     inline     >] sctp_setsockopt_connectx net/sctp/socket.c:1360
 [<ffffffff8592bf36>] sctp_setsockopt+0x226/0x3630 net/sctp/socket.c:3728
 [<ffffffff84d593a5>] sock_common_setsockopt+0x95/0xd0 net/core/sock.c:2642
 [<     inline     >] SYSC_setsockopt net/socket.c:1752
 [<ffffffff84d56548>] SyS_setsockopt+0x158/0x240 net/socket.c:1731
 [<ffffffff85e8eb76>] entry_SYSCALL_64_fastpath+0x16/0x7a
arch/x86/entry/entry_64.S:185
==================================================================

On commit 03891f9c853d5c4473224478a1e03ea00d70ff8d (Jan 11).